check-host-tar.sh: bump minimum tar version to 1.27 for reproducible tar files with...

check-host-tar.sh: bump minimum tar version to 1.27 for reproducible tar files with long paths

Fixes:
http://autobuild.buildroot.net/results/b18/b187e64a61918f17f69588e2355a03286bc5808e

tar 1.27 subtly changed the tar format when a GNU long link entry is added
(which is done for path elements > 100 characters).  The code used to set
the permission mode of the link entry to 0:

  header = start_private_header ("././@LongLink", size, time (NULL));
  FILL (header->header.mtime, '0');
  FILL (header->header.mode, '0');
  FILL (header->header.uid, '0');
  FILL (header->header.gid, '0');
  FILL (header->header.devmajor, 0);
  FILL (header->header.devminor, 0);

This got dropped in 1.27 by commit df7b55a8f6354e3 (Fix some problems with
negative and out-of-range integers), so the settings from
start_private_header() are used directly - Which are:

  TIME_TO_CHARS (t < 0 ? 0 : min (t, MAX_OCTAL_VAL (header->header.mtime)),
		 header->header.mtime);
  MODE_TO_CHARS (S_IFREG|S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH, header->header.mode);
  UID_TO_CHARS (0, header->header.uid);
  GID_TO_CHARS (0, header->header.gid);

The end result is that tar >= 1.27 sets mode to 644.

The consequence of this is that we create different tar files when long path
names are encountered (which often happens when a package downloads a
specific sha1 from a git repo) depending on the host tar version used,
causing hash mismatches.

As a workaround, bump our minimum tar version to 1.27.  It would be nicer to
only do this if we have packages from bzr/git/hg enabled, but that is an
exercise for later.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>